This application focuses on research training in the area of fetal and neonatal physiology. My major area of interest is in regulation of pulmonary vascular tone in the fetus and newborn, and the role of the pulmonary mast cell and its contents in influencing pulmonary vascular reactivity in the perinatal period. The training program will be divided into two phases. Phase I will include 1) a series of didactic courses designed to strengthen and broaden my knowledge base and emphasize background areas of research design, and 2) a carefully designed program of fundamental laboratory experience which will emphasize the development of necessary skills such as surgical preparations in the mother, fetus and newborn, post operative management and chronic care of animals, use and maintenance of physiologic recording equipment and basic concepts of experimental design and hypothesis testing. Phase II will allow me to apply laboratory-based research in more independent investigations under the continuing guidance of my sponsors. These investigations will focus on the area of fetal mast cell development and their influence on pulmonary vascular tone prenatally and postnatally. The role of mast cell degranulation and release of vasoactive agents in mediating or potentiating postnatal pulmonary vasoconstriction seen after fetal hypoxia will also be investigated. These studies will be structured to provide information about the regulation of pulmonary vascular tone in the perinatal period by correlating physiologic changes in pulmonary vascular reactivity with structural changes in mast cells.